Line-scanning optical printer

ABSTRACT

A line-scanning optical printer, which forms an image on a sensitized sheet ( 25 ) by projecting a linear light having a given width and length thereto while successively scanning individual lines in the direction of the width, comprises a casing ( 50 ) having light shielding properties and including a window portion for radiating the linear light to the outside, a light emitting element ( 60 ), which substantially functions as a point light source and is stored in the casing, an optical system ( 72, 71, 73 ) for guiding light from the light emitting element ( 60 ) as the linear light to the window portion, and a liquid crystal optical shutter ( 80 ) attached to the window portion.

TECHNICAL FIELD

The present invention relates to a line-scanning optical printer, inwhich sensitized paper is scanned by means of a scanning head so thatthe sensitized paper is exposed to a linear light with a given width andlength projected from the scanning head, whereby an image is formed.

BACKGROUND ART

Video printers are spread as a type of line-scanning optical printers,whereby a digitally processed image on a display is printed on asensitized sheet. The video printers may be based on any of printsystems including a thermal system, ink jet system, laser beam scanningsystem, liquid crystal shutter system, etc. Among these systems, theliquid crystal shutter system is watched as the best suited one for asmall-sized, lightweight printer. An example of a video printer of theliquid crystal shutter type is disclosed in Japanese Patent ApplicationLaid-open No. 2-287527.

The disclosed video printer will now be described with reference to FIG.21.

A casing 101 contains therein a film loading portion 102 for holding afilm pack FP that is stored with a large number of self-processing filmsF. Further, conveyor roller means 106 is located adjacent to an aperture103 of this film loading portion 102. The conveyor roller 106 iscomposed of a pair of rim drive rollers 104 a and 104 b, which holdstherebetween and draw out a specified film F from the film pack FP inthe film loading portion 102, and a pair of squeezing rollers 105 a and105 b for developing the film F after exposure for recording.

An exposure recording portion 107 for forming an image on the film F islocated between the rim drive roller pair 104 a and 104 b and thesqueezing roller pair 105 a and 105 b. The exposure recording portion107 includes a light source 108 such as a halogen lamp. The film F isexposed to light emitted from the light source 108 and transmittedthrough an optical fiber bundle 109, a color filter (not shown) havingthree colors, R, G and B, which are arranged parallel to one another inan image sub-scanning direction, a liquid crystal light bulb 110, and arefractive index distribution lens array 111.

Polarization plates are arranged individually on the upper and lowersurface portions of the liquid crystal light bulb 110, having theirdeflecting directions in parallel relation. On the other hand, a firstglass substrate is located inside the polarization plates. The colorfilter (not shown), having thin films of three colors, R, G and B,deposited thereon by vacuum evaporation, is formed on one surfaceportion of the first glass substrate, while a plurality of pixelelectrodes, in which transparent electrodes are linearly arranged alongthe color filter (not shown), that is, in the sub-scanning direction,are formed on the other surface portion.

A liquid crystal, such as a twisted nematic liquid crystal, is sealedbetween the pixel electrodes and a second glass substrate. In this case,a common electrode, a transparent electrode, is formed on the secondglass substrate side of a boundary surface between the second glasssubstrate and the liquid crystal by vacuum evaporation. The polarizationplates are arranged on the other surface portion side of the secondglass substrate. Light transmitted through the polarization platespasses through the refractive index distribution lens array 111, wherebythe film F is exposed.

As described above, the conventional line-scanning optical printer isdesigned so that the film F is exposed to the light emitted from thelight source 108 and transmitted through the color filter (not shown)having three colors, R, G and B, which are arranged parallel to oneanother in the image sub-scanning direction, the liquid crystal lightbulb 110, and the refractive index distribution lens array 111 by meansof the optical fiber bundle 109. With this arrangement, not only themembers constituting the optical system are costly but also assemblinginvolves a number of complicated processes thereby increasing the totalcost of the apparatus.

Conventionally, therefore, avoiding the use of a costly optical fiberbundle, there has been used an optical device manufactured by utilizingan optical system that is composed of a lens, concave mirror, flatmirror, etc., which can be formed of plastics at low cost. According tothis conventional optical device, however, an image is formed on a sheetby utilizing a spot light source, so that the quantity of light emittedfrom the spot light source cannot be distributed uniformly. Thus,unevenness in brightness is caused such that the central portion of thespot light source is brighter than the peripheral portion.

DISCLOSURE OF THE INVENTION

The object of the present invention is to provide a line-scanningoptical printer capable of obtaining uniform-density images withoutentailing unevenness in brightness, incorporating a low-cost opticaldevice constituting an optical system made available with low-costconstituent members and reduced number of assembly processes.

In order to achieve the above object, a line-scanning optical printeraccording to the present invention, which is designed to form an imageon a sensitized material by projecting a linear light having a givenwidth and length thereto while successively scanning individual lines inthe direction of the width, comprises a casing having light shieldingproperties and including a window portion for radiating the linear lightto the outside, a light emitting element which substantially functionsas a point light source and is stored in the casing, an optical systemfor guiding light from the spot light source or light emitting elementas the linear light to the window portion, and a liquid crystal opticalshutter attached to the window portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a line-scanning optical printeraccording to the present invention shortly after the beginning of theprinting operation,

FIG. 2 is a perspective view of the optical printer shown in FIG. 1, atthe end of the printing operation;

FIG. 3 is a sectional view taken along line A—A of FIG. 1;

FIG. 4 is an enlarged view showing a portion surrounded by a circle E ofFIG. 3;

FIG. 5A is a top interior view of a scanning head of the optical printershown in FIG. 3, with its cover removed;

FIG. 5B is a sectional view taken along line F—F of FIG. 5A, in whichthe scanning head is fitted with the cover;

FIG. 6A is a sectional view taken along line G—G of FIG. 5A;

FIG. 6B is an enlarged view showing a portion surrounded by a circle Kof FIG. 5B;

FIG. 7A is a front view of an assembly of an optical mask member and alight emitting element holder taken along line L—L of FIG. 5B;

FIG. 7B is a top view corresponding to FIG. 7A;

FIG. 7C is a sectional view taken along line M—M of FIG. 7A;

FIG. 8A is a sectional view taken along line H—H of FIG. 5A;

FIG. 8B is a sectional view taken along line J—J of FIG. 5A;

FIG. 9 is a sectional view taken along line D—D of FIG. 2;

FIG. 10 is a sectional view taken along line A—A of FIG. 1, showing onemodification of an embodiment shown in FIG. 3;

FIG. 11 is an enlarged view showing a portion surrounded by a circle Eof FIG. 10;

FIG. 12 is a diagram for illustrating the basic configuration of anoptical printer shown in FIG. 10;

FIG. 13 is a diagram for illustrating a state where a print scanningholder cover is going to be attached and fixed to a sensitized sheettray holder;

FIG. 14 is an enlarged view showing a portion surrounded by a circle Gof FIG. 13;

FIG. 15 is a diagram for illustrating a state where the print scanningholder cover has already been attached and fixed to the sensitized sheettray holder;

FIG. 16 is an enlarged view showing a portion surrounded by a circle Jof FIG. 15;

FIG. 17 is a sectional view taken along line D—D of FIG. 2, showing thesame modification as the one shown in FIG. 10;

FIG. 18 is a view showing an outline of an optical printer fitted with acleaning member for cleaning a protective glass of an optical shutter;

FIG. 19A is a front view of the cleaning member shown in FIG. 18;

FIG. 19B is a side view of the cleaning member shown in FIG. 18;

FIGS. 20A to 20C are diagrams for illustrating the operation of theoptical printer of FIG. 18; and

FIG. 21 is a sectional view showing a prior art example of aline-scanning optical printer.

BEST MODE FOR CARRYING OUT THE INVENTION

An outline of the configuration and operation of a line-scanning opticalprinter according to the present invention will now be described withreference to FIGS. 1 and 2. The optical printer described below isconnected to a video apparatus that generates video signals, and is usedto print a displayed picture on a sheet or is used as a video printer.

A sensitized sheet tray 20 is installed in a housing 10 so that it canbe taken in and out like a drawer. Facing the photosensitive surface ofa sensitized sheet 25 that is loaded in the sensitized sheet tray 20, ascanning head 40 is mounted for reciprocation in the directions ofarrows B and C. The scanning head 40 constitutes a device for convertingelectrical signals into light signals in the optical printer shown inFIG. 1.

FIG. 1 shows a state in which the sensitized sheet 25 is exposed forprinting as the scanning head 40 is run a short distance in thedirection of arrow B from its home position.

The scanning head 40 further runs in the direction of arrow B from theposition shown in FIG. 1, making the sensitized sheet 25 exposed to thelight for printing. When the exposure for printing is finished, thescanning head 40 then goes back in the direction of arrow C that isopposite to the direction of arrow B and returns to the home position.The sensitized sheet 25, having a latent image of the picture formedthereon by the exposure for print, undergoes development process, and isdischarged through a sensitized sheet exit 22 in the front face.

An outline of the configuration of the aforementioned optical printerwill further be described with reference to FIG. 3.

The housing 10 is fitted with the sensitized sheet tray 20 so as to betaken in and out like a drawer. The sensitized sheet tray 20 is loadedwith a sensitized sheet pack 24. The sensitized sheet pack 24 is storedwith a plurality of sensitized sheets 25 with their photosensitivesurfaces facing upward. Each sensitized sheet is made of a film with aself-developing solution applied thereon.

The sensitized sheet tray 20 is provided with a knob 21 for drawing itout of the housing 10, the sensitized sheet exit 22 through which eachprinted sensitized sheet 25 is discharged, and sensitized sheetdischarging rollers 23 for developing the sensitized sheet 25, havingthe latent image of the picture formed thereon by the exposure forprint, and delivering it to the outside through the sensitized sheetexit 22.

Further, an optical print unit 30 is stored in the housing 10. Theoptical print unit 30 includes a control circuit 31 for controlling theoptical printer, the scanning head 40 for use as a device for convertingelectrical signals into light signals and radiating them and convertingelectrical signals for the formation of the picture on the sensitizedsheet 25 into light signals, a scanning motor (not shown) forreciprocating the scanning head 40 for scanning along the surface of thesensitized sheet 25, a pulley 32 adapted to be engagedly rotated by thescanning motor, and a scanning wire 33 engaged with the scanning head 40and adapted to convert a rotary motion of the pulley 32 into a linearmotion, thereby reciprocating the scanning head 40 for scanning alongthe surface of the sensitized sheet 25.

An outline of the configuration of the scanning head 40 will further bedescribed with reference to the enlarged view of FIG. 4.

The scanning head 40 includes a casing 50, which is formed so as not toallow inside light to leak out. The casing 50 is composed of a casingbody 51 and a cover 57. Scattered light preventing projections 58 areformed individually on the respective inner wall surfaces of the casingbody 51 and the cover 57.

The casing 50 contains therein a light emitting element 60, an opticalsystem, and an optical shutter 80. The light emitting element 60substantially functions as a point light source that emits light towhich the sensitized sheet 25 is to be exposed. The optical systemconverts the light emitted from the light emitting element 60 into anarrow rectilinear parallel light which is radiated toward thesensitized sheet 25. The optical shutter 80 includes a plurality ofshutter elements, which are arranged in a straight line along theparallel light radiated from the optical system to cut off transmissionof the light for each unit area in accordance with an electrical signal,thereby forming pixels on the sensitized sheet 25.

A liquid crystal is used as the optical shutter. The liquid crystaloptical shutter 80 is mounted from outside the casing 50, and is coveredby a protective member 83 that is fixed to the casing body 51. As shownin FIG. 8A, the protective member 83 is formed with a window throughwhich light from the optical shutter 80 is transmitted to the sensitizedsheet 25, and a protective glass 82 is attached to the window portion.The window portion is provided on a surface extending substantiallyparallel to a plane that contains the light emitting element 60 and aspherical concave mirror 71 (mentioned later). Further, the liquidcrystal optical shutter 80 is supplied with a driving signal from thecontrol circuit 31 through a first FPC (flexible printed circuit) 84.The optical shutter 80 and the first FPC 84 are fixed to the casing 50by attaching the protective member 83 to the casing body 51 of thecasing 50, as shown in FIG. 8B. In FIG. 8A, numeral 81 denotes a matchmember that is attached to the liquid crystal optical shutter 80.

The light emitting element 60 is composed of LEDs of at least threecolors, R (red), G (green), and B (blue). The light emitted from thelight emitting element 60 is converted into the narrow rectilinearparallel light and radiated onto the sensitized sheet 25. Power to thelight emitting element 60 is supplied through a second FPC 85 (see FIG.7B).

An optical system of the scanning head 40 is composed of a toroidal lens72, the spherical concave mirror 71, and a plane mirror 73. The lowerhalf of the lens 72 functions as an optical path changing lens forrefracting the light emitted horizontally from the light emittingelement 60 substantially functioning as a point light source, toward thespherical concave mirror 71. The upper half of the lens 72 has afunction to refract the light converted into the substantiallyrectilinear parallel light in the horizontal direction so that it isfocused on the photosensitive surface of the sensitized sheet 25. Themirror 71 serves to convert the light transmitted through the opticalpath changing lens, which is formed integrally with the lower half ofthe toroidal lens 72, into a substantially rectilinear parallel light inthe horizontal direction and reflect it. The mirror 73 serves to convertthe substantially horizontal light transmitted through the toroidal lens72 substantially in the vertical direction and reflect it toward thesensitized sheet 25 thereunder.

The configuration of this optical system will further be described withreference to FIGS. 5A and 5B.

As shown in FIG. 5B, a window portion 52 is formed on the undersurfaceof the casing 50. As shown in FIG. 7B, moreover, the casing 50 containsa fixed assembly that includes the light emitting element 60,substantially functioning as a point light source that emits the lightto which the sensitized sheet 25 is exposed, a light emitting elementsubstrate 61 on which the light emitting element 60 is fixed, a lightemitting element holder 62 on which the light emitting element substrate61 is fixed so that the light emitting element 60 is held in a fixedposition in the casing 50, and an optical mask member 63 for partiallyrestricting the passage of the light that is emitted from the lightemitting element 60.

The substrate 61, which transmits light, is attached to the casing 50 sothat its outer and inner surfaces are exposed to the outside and insideof the casing 50, respectively, and supplies electric power to the lightemitting element 60 from outside the light emitting element 60 throughthe second FPC 85 that is connected to a connector on the side exposedoutside of the substrate 61.

Further, the casing 50 incorporates the spherical concave mirror 71 forconverting the light emitted from the light emitting element 60,substantially functioning as a point light source, into thesubstantially rectilinear parallel light, the toroidal lens 72 forrefracting the light converted into the substantially rectilinearparallel light by means of the spherical concave mirror 71 so that it isfocused on the photosensitive surface of the sensitized sheet 25, andthe plane mirror 73 for refracting the substantially horizontal light,transmitted through the toroidal lens 72, substantially in the verticaldirection toward the sensitized sheet 25 thereunder.

Two opposite end portions of the spherical concave mirror 71, which isarcuated in the lengthwise direction of the rectilinear parallel light,are held between concave mirror support portions 53 and backup springsupport 54, which are formed at two positions on the casing body 51, bymeans of concave mirror backup springs 90, which will be mentionedlater.

The optical shutter 80, which includes a plurality of shutter elementsarranged in a straight line along the parallel light radiated from theoptical system and capable of cutting off transmission for each unitarea in accordance with an electrical signal, thereby forming pixels onthe sensitized sheet 25, is attached to the undersurface of the casingbody 51 so as to close the window portion 52. Thus, not only the cost ofthe constituent members of the optical system but also the number ofassembly processes can be reduced. The optical shutter 80 is protectedby means of the protective glass 82 (see FIG. 8B). Light transmittedthrough the optical shutter 80 passes through the protective glass 82and reaches the sensitized sheet.

Referring now to FIGS. 5A to 6B, there will be described a state inwhich the spherical concave mirror 71 is attached to the casing body 51.

The opposite end portions of the arcuate concave mirror 71 are heldrespectively between the concave mirror support portions 53 and thebackup spring support portions 54, which are formed in the two positionson the casing body 51, by means of the concave mirror backup springs 90,which will be mentioned later. As shown in FIG. 6A, a projection 71 a isformed on each end portion of the spherical concave mirror 71. Theprojections 71 a abut respectively against the concave mirror supportportions 53 that are formed at the two positions on the casing body 51.The spherical concave mirror 71 are pressed against the concave mirrorsupport portions 54 by means of the concave mirror backup springs 90that are inserted and fixed respectively in hole portions of the backupspring support portions 54 that are formed at the two positions on thecasing body 51.

As shown in FIG. 6B, moreover, a concave mirror support spring 91, ahelical compression spring, is interposed between the undersurface ofthe central portion of the spherical concave mirror 71 and the casingbody 51, and pushes up the central portion of the spherical concavemirror 71.

An inclination adjusting member 92 is screwed into the cover 57 of thecasing body 50. The spherical concave mirror 71 is designed so that itscentral portion can be pressed down against the lifting force of theconcave mirror support spring 91 as the inclination adjusting member 92is screwed in further. Thus, the position for irradiation can be easilyadjusted to the position of the optical shutter 80 by regulating thelength of engagement of the inclination adjusting member 92.

Referring to FIGS. 5A and 5B, there will be described a state in whichthe toroidal lens 72 is attached to the casing body 51.

The casing body 51 is formed with toroidal lens end support portions 55b and also with toroidal lens center support portions 55 a at two placesrespectively. In installing the toroidal lens 72 to the casing body 51,the toroidal lens 72, which is formed straight, is slightly curved as itis inserted between the two toroidal lens end support portions 55 b andthe two toroidal lens center support portions 55 a. Thereupon, thetoroidal lens 72 is fixed to the casing body 51 by means of its ownelasticity.

Thus, the toroidal lens 72 may be formed straight, with the result thata molding tool can be manufactured at low cost. Since the toroidal lens72 can be installed to the casing body 51 by being inserted between thetoroidal lens end support portions 55 b and the toroidal lens centersupport portions 55 a, moreover, its assembly is easy.

Referring to FIGS. 7A to 7C, there will be described the construction ofthe assembly that includes the light emitting element substrate 61 onwhich the light emitting element 60 is fixed, the light emitting elementholder 62 for holding the light emitting element substrate 61, and theoptical mask member 63 for partially restricting the passage of thelight that is emitted from the light emitting element 60.

The light emitting element holder 62 is fitted with the light emittingelement substrate 61 that fixedly holds the light emitting element 60and also with the optical mask member 63. The optical mask member 63 isformed with a slit-shaped aperture 64. The aperture 64 has wide oppositeend portions with a width Ww and a narrow central portion with a widthWn.

Referring now to FIG. 5A, there will be described the reason why theaperture 64 of the optical mask member 63 is formed having the wideopposite end portions with the width Ww and the narrow central portionwith the width Wn. The light emitted from the light emitting element 60,which is radiated in a wide circle around the front face, has higherluminous intensity in the central portion and lower luminous intensityin the periphery. Thus, if the light emitted from the light emittingelement 60 is allowed to directly reach the sensitized sheet 25 as animage forming area, the density varies between the central portion andperipheral portion of the image, so that the image quality lowers. Auniform-density image can be obtained, therefore, by restricting thehigher-intensity light in the central portion more than the light in theperiphery in order to eliminate the unevenness of the image density.

Referring to FIGS. 5A and 5B, there will be described a structure forattaching a flat mirror 73 to the casing body 51.

As shown in FIG. 5A, a left-hand flat mirror support portion 56 a, aright-hand flat mirror support portion 56 b, and flat mirror hold-downportions 56 c opposite the support portions 56 a and 56 b are formedrespectively in those parts which are located close to two opposite endportions of the flat mirror 73.

Referring to FIGS. 8A and 8B, there will be described a state in whichthe flat mirror 73 is attached to the casing body 51.

As shown in FIG. 8A, the left-hand end portion of the flat mirror 73 isheld between the left-hand flat mirror support portion 56 a and thecorresponding flat mirror hold-down 56 c, while as shown in FIG. 8B, theright-hand end portion of the flat mirror 73 is held between theright-hand flat mirror support portion 56 b and the corresponding flatmirror hold-down portion 56 c.

Two projections (see FIG. 8A) for supporting the left-hand end portionof the flat mirror 73 are formed on the left-hand flat mirror supportportion 56 a, while one projection (see FIG. 8B) for supporting theright-hand end portion of the flat mirror 73 is formed on the right-handflat mirror support portion 56 b. Thus, the flat mirror 73 are pressedagainst the two projections on the left-hand flat mirror support portion56 a and the one projection on the right-hand flat mirror supportportion 56 b by means of the flat mirror hold-down portions 56 c so asto be held between them, that is, the flat mirror 73 is supported bymeans of the three projections in all. Therefore, even if the threeprojections differ in height, the flat mirror 73, can be kept fixedbecause it is pressed equally against the three projections as it isheld between them.

Referring now to FIGS. 3 and 4, there will be described the operation ofthe optical printer constructed in the aforesaid manner.

First, the optical printer is connected to the video apparatus (notshown) that generates video signals, the power source of the opticalprinter is turned on, and the sensitized sheet tray 20 set in thehousing 10 is drawn out with a hand by pulling the knob portion 21. Thesensitized sheet tray 20 is loaded with the sensitized sheet pack 24that is packed with a plurality of sensitized sheets 25, and is set inthe housing 10.

If a print command is given in this state, the light emitting element 60emits light, and the light emitted from the light emitting element 60 isreflected to be converted into the substantially rectilinear parallellight by the spherical concave mirror 71. The light converted into thesubstantially rectilinear parallel light by the spherical concave mirror71 is refracted by the toroidal lens 72 so that it is focused on thephotosensitive surface of the sensitized sheet 25. The substantiallyhorizontal light transmitted through the toroidal lens 72 is refractedsubstantially in the vertical direction by being reflected by the flatmirror 73 and projected to the photosensitive surface of the sensitizedsheet 25, although the light is usually intercepted by means of theoptical shutter 80.

When a video signal is delivered from the video apparatus to the opticalprinter, the control circuit 31 actuates the scanning motor (not shown)to rotate the pulley 32, and causes the scanning wire 33 to move thescanning head 40 at its home position shown in FIGS. 1 and 3 in thedirection of arrow B in FIG. 1 at a constant speed. At the same time,the control circuit 31 outputs an optical shutter driving signal inaccordance with the video signal, thereby actuating the shutter elementsof the optical shutter 80, which are arranged in a straight line in adirection perpendicular to the moving direction of the scanning head 40,to transmit the light selectively.

First, a latent image of a first pixel line is formed. As the scanninghead 40 moves further, latent images of second and third pixel lines areformed successively on the photosensitive surface of the sensitizedsheet 25. When the scanning head 40 reaches its end point shown in FIGS.2 and 9, the latent image of the picture is completed. After reachingthe end point, the scanning head 40 returns to the home position shownin FIGS. 1 and 3. The sensitized sheet 25, having the latent image ofthe picture formed thereon, is developed by means of the sensitizedsheet discharging rollers 23 as it is sent out through the sensitizedsheet exit 22.

According to the present invention constructed in the manner describedabove, the optical system is composed of the concave mirror, toroidallens, and flat mirror. Thus, the constituent members of the opticalsystem are available at low costs, and the number of assembly processescan be reduced, so that a low-priced electrical-to-optical signalconverter can be obtained.

Referring now to FIGS. 10 to 17, there will be described onemodification of the optical printer described above with reference toFIGS. 3 to 9.

An outline of the configuration of this optical printer will bedescribed with reference to FIGS. 10 and 11. A sensitized sheetprocessing unit 42 and an optical print unit 30 are incorporated in thehousing 10.

The sensitized sheet processing unit 42 is composed of a sensitizedsheet tray 20, which is used to load a sensitized sheet pack 24 that isstored with a plurality of sensitized sheets 25, and a sensitized sheettray holder 26 (see FIG. 12), which holds the sensitized sheet tray 20in a manner such that the tray 20 can be drawn out. The front face ofthe sensitized sheet tray 20 is formed with a knob portion 21 fordrawing out the tray 20 from the housing 10 and a sensitized sheet exit22 through which each printed sensitized sheet 25 is discharged. Furtherprovided are sensitized sheet discharging rollers 23 that are used todevelop the sensitized sheet 25 where a latent image of a picture hasbeen formed by exposure for print, and deliver it to the outside throughthe sensitized sheet exit 22.

As shown in FIGS. 10 and 12, the optical print unit 30 is composed of aprint scanning holder 34 as a casing and a print scanning holder cover35 as a cover member. The print scanning holder 34 contains therein ascanning head 40 for use as an electrical-to-optical signal converterfor converting electrical signals into light signals and radiating themand forming an image on each sensitized sheet 25, a print scanningmechanism (including a scanning wire 33 and a pulley 32) forreciprocating the scanning head 40 for scanning in the longitudinaldirection or in the horizontal direction in FIG. 10 along the surface ofthe sensitized sheet 25, and a control circuit 31 for controlling theoptical printer.

An outline of the configuration of the scanning head 40 will bedescribed with reference to FIG. 11.

The scanning head 40 comprises a casing 50 formed so as to preventinside light from leaking out, a light emitting element 60 and anoptical system arranged in the casing 50, and an optical shutter 80located outside the undersurface of the casing 50.

The light emitting element 60 substantially functions as a point lightsource that emits light to which the sensitized sheet 25 is to beexposed. Light emitted from the light emitting element 60 is convertedinto a narrow rectilinear parallel light by means of the optical system(toroidal lens 72, spherical concave mirror 71, and flat mirror 73), andis radiated toward the sensitized sheet 25. The optical shutter 80comprises a plurality of shutter elements arranged to cut offtransmission for each unit area in accordance with an electrical signal,thereby forming pixels on the sensitized sheet 25.

A description of the optical system is omitted since it is identicalwith the one described before with reference to FIGS. 3 and 4.

Referring now to FIG. 12, there will be described the respectiveconfigurations of the optical print unit 30 and the sensitized sheettray holder 26.

The sensitized sheet processing unit 42 and the optical print unit 30,each being constructed as an individual unit, are combined together, anda housing lower-half portion 10 a and a housing upper-half portion 10 bare attached to them.

The sensitized sheet processing unit 42 is obtained by attaching thesensitized sheet tray 20 to the sensitized sheet tray holder 26.Further, the optical print unit 30 is composed of the print scanningholder 34, which is fitted with the scanning head 40, and the printscanning holder cover 35.

More specifically, the print scanning holder 34, as the casing of theoptical print unit 30, is attached to the sensitized sheet tray holder26. Thus, the sensitized sheet tray holder 26 serves as the base of theprint scanning holder 34 as the casing. FIG. 12 shows a state in whichthe sensitized sheet tray 20 is loaded with the sensitized sheet pack24. The sensitized sheet pack 24 is packed with a plurality ofsensitized sheets 25 with their photosensitive surfaces facing upward.

Referring now to FIGS. 13 to 16, there will be described steps ofprocedure for fixing the optical print unit 30 to the sensitized sheettray holder 26 as the base.

As shown in FIGS. 13 and 14, the print scanning holder 34 is firstinstalled in the sensitized sheet tray holder 26. Then, a base engagingportion 37 a that is formed on the print scanning holder cover 35 iscaused to engage a cover retaining portion 36 a that is formed on thesensitized sheet tray holder 26.

Then, the print scanning holder cover 35 is rotated around the baseengaging portion 37 a in the direction of arrow H of FIG. 13, whereuponit is put on the print scanning holder 34, as shown in FIGS. 15 and 16.Subsequently, a base fixing portion 37 b (see FIG. 13), which is formedon the end portion of the print operation holder cover 35 which issituated opposite to the end portion having the base engaging portion 37a thereon, is fixed to a cover fixing portion 36 b on the sensitizedsheet tray holder 26 by means of fixing means 38 such as a screw. Thefixing means 38 may be any other fixing member than a screw.

With use of the mounting structure described above, the print scanningholder 34, for use as the casing, can be attached and fixed to thesensitized sheet tray holder 26, as the base, without using any fixingmember such as a screw.

According to the one modification described above with reference toFIGS. 10 to 17, the casing is mounted on the base in a manner such thatthe cover engaging portion and the base fixing portion each provided onthe cover are caused to engage the cover retaining portion and the coverfixing portion each provided on the cover, respectively. Therefore, itis unnecessary to use the fixing member for attaching the casing to thebase and the fixing member for attaching the cover to the casing, sothat the number of components to be used can be reduced, and the cost ofthe apparatus can be lowered as a whole.

Further, there is no need of mounting work for mounting the casing onthe base or mounting the cover on the casing by means of a fixing memberor the like. Thus, the operating time is shortened, so that the workefficency is improved.

Referring now to FIGS. 18 to 20, there will be described an arrangementof a mechanism for cleaning the outer surface (surface opposite to thesensitized sheet 25) of the protective glass 82 (see FIG. 8B) forprotecting the optical shutter 80 for preventing rubbish, dirt, dust,etc. from adhering to the outer surface of the protective glass 82 toform lines on the sensitized sheet 25, to degrade the image quality.

FIG. 18 shows an outline of the construction of the optical printer towhich the cleaning member is attached. The construction of the opticalprinter shown in FIG. 18 itself is basically the same as theconstruction of the optical printer shown in FIGS. 1 to 17.

The housing 10 of the optical printer is situated on a platform 93. Thehousing 10 contains therein the casing 50 and a drive mechanism(scanning wire 33 and pulley 32) for the scanning head 40, and isprovided with a cleaning member 94 on its bottom thereof. The housing 10is covered by a top cover 10 b.

The scanning head 40 contains therein an optical mechanism that iscomposed of the light emitting element 60 as an LED light source,toroidal lens 72, spherical concave mirror 71, and flat mirror 73 as areflector. Further, the scanning head 40 is provided with the opticalshutter 80 and the protective glass 82 for protecting the opticalshutter 80.

The platform 93 contains therein the control circuit 31, sensitizedsheet pack 24, and sensitized sheet discharging rollers (developingrollers) 23.

The cleaning member 94 is attached to the bottom portion of the housing10 so as to get into a gap h between the protective glass 82 and theunderside of the housing 10. The cleaning member 94 is arranged so thatit comes into contact with the protective glass 82 under a givenpressure, thereby cleaning the protective glass 82, when the scanninghead 40 is situated in its shunting position mentioned later. Theposition of the scanning head 40 is detected by means of positionsensors 95 a and 95 b.

The following is a description of an outline of the operation of theoptical printer shown in FIG. 18.

The scanning head 40 (scanning head unit) is fed at a fixed speed in thedirection of the arrow of FIG. 18 with respect to the sensitized sheet25 by means of the drive mechanism (scanning wire 33 and pulley 32). Asthis is done, the optical mechanism 12 in the scanning head 40 exposesthe sensitized sheets 25 in succession by line scanning through a window43 on the underside of the housing 10, thereby forming images on thesensitized sheets 25.

The optical shutter 80 includes one scanning electrode and 640 signalelectrodes, whereby 640 pixels are formed in the direction of the widthof the sensitized sheet 25. The sensitized sheet 25 which contains adeveloping solution is discharged to the outside of the platform 93after the developing solution is applied to the photosensitive surfaceby forced contact of the developing rollers 15 and developed.

As shown in FIG. 19B, the cleaning member 94 is composed of a leafspring 96 and a de-electrifying piece 97 fixed to its surface.

The construction of the cleaning member 94 will now be described withreference to FIGS. 19A and 19B.

A contact portion 96 a on the distal end of the leaf spring 96 thatconstitutes the cleaning member 94 is curved so that it can be broughtuniformly into contact with the protective glass 82 throughout itswidth, and a plurality of support branches 96 b, e.g., three in number,are formed near the crosswise opposite ends and on the central portionof the basal part of the leaf spring 96. The leaf spring 96 is formedwith screw holes 96 c for fixation on the housing 10. The height H ofthe curved contact portion 96 a of the leaf spring 96 is set to be alittle larger (H>h) than the gap h (see FIG. 18) between the protectiveglass 82 and the underside of the housing 10. One end portion of theleaf spring 96 is fixed to the bottom portion of the housing 10, whilethe other end portion is made to come into contact with the surface ofthe protective glass 82 under the given pressure throughout the area ofthe contact portion 96 a.

The de-electrifying piece 97 is bonded on the whole area of the contactportion 96 a by adhesive so that the leaf spring 96 can contact thesurface of the protective glass 82 uniformly and securely for obtaininghigh cleaning effect. Static electricity that is produced as the surfaceof the protective glass 82 is rubbed with the de-electrifying piece 97can be transferred to cloth of the piece 97, while rubbish, dirt, dust,etc. are cleared by the cloth. Further, the protective glass 82 and theleaf spring 96, a metallic part, are not directly in contact with eachother, that is, the curved surface of the de-electrifying piece 97 is incontact with the protective glass 82. Therefore, the de-electrifyingpiece 97 will not wear easily, and its life can be prolonged.

The operation of the scanning head 40 and cleaning operation by means ofthe cleaning member 94 will now be described with reference to FIGS. 20Ato 20C.

FIG. 20A shows a state in which the scanning head 40 is in its shuntingposition, that is, an end of the scanning head 40 is situated in a firstposition P1. In this state, both the position sensors 95 a and 95 b areoff.

Thereafter, the scanning head 40 moves in the direction of arrow A,thereby turning on both the position sensors 95 a and 95 b in theposition shown in FIG. 20B. This position is a write start position suchthat the end of the scanning head 40 is situated in a second positionP2. In this state, optical storage of image data in the sensitized sheet25 is started.

The scanning head 40 writes the image data on the sensitized sheet 25 asit further moves in the direction of arrow A for scanning. During thisprocess, both the position sensors 95 a and 95 b are on.

Then, when the scanning head 40 reaches a position shown in FIG. 20C,the position sensor 95 a is turned off, and only the position sensor 95b remains turned on. This state corresponds to a write end position suchthat the end of the scanning head unit is in a third position P3. Inthis state, the storage process of the image data comes to an end,whereupon the scanning head 40 returns to its shunting position or thefirst position P1.

The distance between the second position P2 and the third position P3 isan effective scanning distance L2 of the scanning head 40. In FIG. 20A,L3 designates the scanning distance of the scanning head 40, and L1designates the scanning distance of the scanning head 40 before thestart of writing operation.

In FIG. 20A, the contact portion 96 a of the leaf spring 96 is situatedbetween the first position P1 and the second position P2 but closer tothe second position P2, and the leaf spring 96 is located at the bottomof the housing 10 lest it interfere with the range of the effectivescanning distance L2 of the scanning head 40. Accordingly, cleaning ofthe surface of the protective glass 82 by means of the leaf spring 96 iseffected twice between the first position P1 and the second position P2as the scanning head 40 reciprocates in the direction of arrow A and theopposite direction for scanning. Thus, rubbish, dirt, dust, etc.adhering to the surface of the protective glass 82 can be wiped offthoroughly.

According to the optical printer shown in FIG. 18, as described above,the leaf spring 96 that constitutes the cleaning member 94 is located inthe housing 10 of the optical printer in a manner such that it is incontact with the protective glass 82 while the scanning head unit islocated between its shunting position and the position for the start ofwriting operation, and that it is not in contact with the protectiveglass 82 while the scanning head unit is effectively operating forscanning. Thus, rubbish, dirt, dust, etc. adhering to the protectiveglass surface can be wiped off, so that the image quality will not bedegraded.

Further, the contact portion of the leaf spring 96 is curved and aplurality of support branches are arranged in the width direction sothat the leaf spring 96 can be brought uniformly into contact with thewhole area of the protective glass in the width direction. Thus,rubbish, dirt, dust, etc. adhering to the protective glass surface canbe wiped off evenly.

Furthermore, the contact portion of the leaf spring 96 is provided withthe de-electrifying piece 97 to be brought into contact with theprotective glass surface. Thus, static electricity can be removed, andrubbish, dirt, dust, etc. adhering to the protective glass surface canbe wiped off more securely, so that the image quality will not bedegraded.

What is claimed is:
 1. A line-scanning optical printer designed to form an image on a sensitized material by projecting a linear light while successively scanning individual lines, said line-scanning optical printer comprising: a light shielding casing having a window portion for radiating the linear light to the outside; a light emitting element in the casing, wherein the light emitting element functions as a point light source; an optical system, housed in said light shield casing, for guiding light from the point light source or light emitting element as the linear light to said window portion; and a liquid crystal optical shutter attached to said window portion.
 2. A line-scanning optical printer according to claim 1, wherein said light emitting element is formed of LEDs.
 3. A line-scanning optical printer according to claim 2, wherein said light emitting element is composed of LEDs of at least three colors, R, G and B.
 4. A line-scanning optical printer according to claim 3, wherein said LEDs are mounted on an LED substrate and installed together with the LED substrate inside the casing by means of a holder.
 5. A line-scanning optical printer according to claim 2, wherein said liquid crystal optical shutter is attached from outside of said casing.
 6. A line-scanning optical printer according to claim 5, wherein said liquid crystal optical shutter is fitted with a protective member covering the whole area of the liquid crystal optical shutter except a light transmitting portion.
 7. A line-scanning optical printer according to claim 6, wherein said liquid crystal optical shutter is connected with an FPC for giving an electrical signal for driving a liquid crystal signal.
 8. A line-scanning optical printer according to claim 7, wherein said optical shutter and said FPC are fixed to said casing by attaching said protective member to said casing.
 9. A line-scanning optical printer according to claim 8, wherein said casing is fitted with a light transmitting substrate with the obverse and reverse thereof exposed respectively to the outside and inside of said casing, and electric power is supplied from outside of said light emitting element through the FPC connected to a connector provided on the externally exposed surface side of the substrate.
 10. A line-scanning optical printer according to claim 9, wherein said substrate is internally shielded from light by a cover member.
 11. A line-scanning optical printer according to claim 1, wherein said optical system includes at least a concave mirror, and said linear light is formed by converting the radial light from the point light source or light emitting element into parallel light and reflecting the light by means of the concave mirror.
 12. A line-scanning optical printer according to claim 11, wherein said concave mirror is mounted inside said casing in a manner such that the angle of vertical inclination of the reflective surface thereof is adjustable.
 13. A line-scanning optical printer according to claim 12, wherein said linear light is focused on the sensitized material by means of a toroidal lens.
 14. A line-scanning optical printer according to claim 13, wherein said concave mirror is a spherical concave mirror.
 15. A line-scanning optical printer according to claim 14, wherein said light emitting element, said concave mirror, and said toroidal lens are stored in the casing to form an optical head, and said linear light is radiated to the outside through the window portion formed in the casing.
 16. A line-scanning optical printer according to claim 15, wherein said optical head includes the casing having the window portion for radiating the linear light to the outside, the light emitting element provided in the casing, the concave mirror located in said casing at a distance from said light emitting element in a scanning direction for each said line, and the toroidal lens located so as to transmit the light from said concave mirror in said casing.
 17. A line-scanning optical printer according to claim 16, wherein said window portion of said optical head is provided on a surface parallel to a plane containing said light emitting element and said concave mirror.
 18. A line-scanning optical printer according to claim 17, wherein said optical head further includes a flat mirror for vertically reflecting the light emitted from said light emitting element and reflected by said concave mirror so that the reflected light is guided to said window portion.
 19. A line-scanning optical printer according to claim 18, wherein said flat mirror is located between said toroidal lens and the optical shutter.
 20. A line-scanning optical printer according to claim 19, further comprising an optical path changing lens located between said light emitting element and said concave mirror and capable of refracting the light emitted from said light emitting element so that the light strikes at a specified area in the concave mirror.
 21. A line-scanning optical printer according to claim 20, wherein said toroidal lens is formed integrally with said optical path changing lens.
 22. A line-scanning optical printer according to claim 18, further comprising a mask member located between said concave mirror and said flat mirror, said mask member having an aperture for transmitting the reflected light converted into a linear light by said concave mirror and shielding scattered light.
 23. A line-scanning optical printer according to claim 22, wherein said aperture of said mask member is rectangular, having a narrower central portion and wider end portions.
 24. A line-scanning optical printer according to claim 1, wherein an optical element constituting said optical system changes shape when mounted in said casing.
 25. A line-scanning optical printer according to claim 24, wherein said optical system is a toroidal lens.
 26. A line-scanning optical printer according to claim 25, wherein said toroidal lens changes shape when mounted in said casing such that three portions of said toroidal lens, including both ends and the center, are regulated by means of said casing.
 27. A line-scanning optical printer according to claim 1, wherein said casing has a scattered light preventing projection on the interior wall surface thereof for preventing the light emitted from said light emitting element from scattering.
 28. A line-scanning optical printer according to claim 1, wherein said sensitized material has the form of a sheet.
 29. A line-scanning optical printer according to claim 28, wherein said sensitized material is a film with self-developing solution.
 30. A line-scanning optical printer according to claim 29, wherein an image is formed when said casing moves with respect to said film with self-developing solution.
 31. A line-scanning optical printer according to claim 30, wherein said casing is provided with a cleaning member adapted to reciprocate in a write region set between a write start position in which optical write in said film is started and a write end position in which the optical write is finished, thereby effecting the optical write in said film, and to clean the surface of said liquid crystal optical shutter, which faces the film, in a region other than said write region.
 32. A line-scanning optical printer according to claim 31, wherein said cleaning member is an elastic body fixed to the print scanning holder and adapted to wipe off the surface of said liquid crystal optical shutter, which faces the film, to clean said liquid crystal optical shutter when said casing is moved to a position other than the write region.
 33. A line-scanning optical printer according to claim 32, wherein said cleaning member is provided with a de-electrifying piece on a portion of said cleaning member, wherein said delectrifying piece contacts the surface of a protective glass so as to protect the liquid crystal optical shutter, which faces the film.
 34. A line-scanning optical printer according to claim 30, wherein said casing and said film with self-developing solution are superposed on each other so that the whole area of said film can be scanned with said window portion as said casing moves.
 35. A line-scanning optical printer according to claim 34, wherein said casing and said film are stored, respectively, in a print scanning holder and a sensitized sheet tray holder constructed independently of each other, the print scanning holder being provided with a casing drive mechanism and a drive control circuit board for moving said casing with respect to said film.
 36. A line-scanning optical printer according to claim 35, wherein said print scanning holder has a space over said sensitized sheet tray holder said space containing said casing and said casing drive mechanism therein when caused to overlap said sensitized sheet tray holder and a space partially covering said sensitized sheet tray holder side, situated beside said film, and said space containing said drive control circuit board therein.
 37. A line-scanning optical printer designed to form an image on a sensitized material by projecting a linear light while successively scanning individual lines said line-scanning optical printer comprising: a platform having therein a sensitized sheet pack stored with a plurality of sensitized sheets, a sensitized sheet discharge mechanism and a circuit board; a housing fixedly placed on said platform; a scanning head located in said housing; and a scanning head drive mechanism for rectilinearly reciprocating the scanning head in the housing, said scanning head including a casing having a window portion formed in part of the underside thereof, a light emitting element which functions as a point light source and is stored in said casing, an optical system for causing light from the light emitting element, as the linear light, to pass through the window portion of said casing, and an optical shutter mounted facing the window of said casing, the optical shutter being capable of operating in response to a driving signal from said circuit board.
 38. A line-scanning optical printer according to claim 37, wherein said light emitting element is located in the center of the casing with respect to the moving direction of the casing, and the light emitted from the light emitting element first advances in the moving direction of the casing, is reflected by a concave mirror fixed to one end portion of the casing, then advances in the direction opposite to the moving direction of the casing, is reflected by a reflector fixed near the other end portion of the casing, and then advances toward a sensitized sheet through the window of the casing.
 39. A line-scanning optical printer designed to form an image on a sensitized material by projecting a linear light onto the sensitized material while successively scanning individual lines across the sensitized material, said line-scanning optical printer comprising: a light shielding casing having a window portion for radiating the linear light externally to the casing; a light emitting element in the casing, wherein the light emitting element functions as a point light source and is positioned in the casing; an optical system for guiding light originating from the point light source or light emitting element as the linear light to said window portion and positioned within said casing; and a liquid crystal optical shutter positioned in an optical path of said optical system and attached to the window portion. 